A major problem of the world today is finding safe and acceptable food for an ever-increasing population. All foods are extremely chemical entities even in their natural state. Many commonly used foodstuffs naturally contain toxic principals in small amounts. Farmers are the major producers of food we eat. Most of those foods are contaminated with different poisonous chemicals used in farming practices. Foods today are increasingly getting polluted by industrial pollutants, accidentally during processing and through the act of adulteration. The present century has witnessed the world-wide rise of new chemical hazards from food. Food is at risk and we eat at our peril.
Poison is very difficult to define and many substances present in food would have adverse or toxic effects if taken in large loses. In the words of Paracelsus (1493-1541): “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy.” Toxic matters are foreign substances. They differ greatly in their chemical nature and their fate in our bodies also varies. In general, a substance may follow one of the five possible sequences, each of which has variants.
1. It may pass through the gastrointestinal tract unabsorbed. Pectin and other food thickeners are examples. It may be digested by enzymes in the upper gastrointestinal (GI) tract or broken down by enzymes in the colon. Even if a substance is not absorbed it can affect the motility of the GI tract and cause vomiting, diarrhoea or constipation.
2. A substance may be absorbed and pass into the portal vein to the liver, where it may be metabolized and then excreted back into the GI tract in bile and the sequence may be repeated.
3. Water-soluble substances may be absorbed and pass through the liver into the general circulation. In the blood the substance may be partly bound to one of the plasma proteins, but it is excreted by kidneys and passes into urine. If such a substance should be oncogenic, the organ most likely to be affected is the urinary balder.
4. Fat-soluble substances after absorption reach the liver and get metabolized in two stages. Usually the metabolites are more water soluble and more easily excreted and less toxic.
5. Some substances may be absorbed but neither metabolized nor excreted. They stay in the body and get accumulated. Even if harmless in small amounts in acute and subacute tests, they may lead to long-term harmful effects. Examples are fatsoluble compounds like DDT and PBB (polybrominated biphenyl). These are not only stored in the adipose tissue but pass into the milk fat in lactating women. Substances like calcium can stay in bones for a long time.
Natural toxins are toxic compounds that are naturally produced by living organisms. Interestingly, these toxins are not harmful to the organisms themselves, but they may be toxic to other creatures, including humans, when consumed. Some toxins are produced by plants as a natural defense mechanism against predators, insects or microorganisms or as a consequence of infestation with microorganisms, such as mould. Other sources of natural toxins are microscopic algae and plankton in oceans or sometimes in lakes that produce chemical compounds called aquatic biotoxins. They are toxic to humans but not to fish or shellfish (such as mussels, scallops and oyster) that eat these toxin producing organisms.
Concentrations of algae in our oceans and lakes have longed bloomed naturally, but climate change and fertilizer runoff from farms have exacerbated the situation in recent years. The most dangerous of the blooms, called harmful algal blooms (or HABs) are often reddish in colour, leading observers to call them red tides. Some of the algae or phytoplankton manufacture saxitoxin, a poison so devastating it is the underlying cause of paralytic shellfish poisoning, an often-lethal reaction to shellfish that are storing toxic algal cells.
Other phytoplankton produce domoic acid, a neurotoxin that kill people birds and marine mammals snacking on contaminated fish and shellfish. Other than paralysis, algal toxin can cause diarrhoea and vomiting also. Another example is ciguatera fish poisoning which is caused by consuming fish contaminated with dinoflagellates that produce ciguatoxins.
Health and fitness experts often emphasize on seafood for muscles, high proteins and weight loss. But seafood is responsible for a large portion of food borne diseases. Some of the pathogens responsible for sea food infections are vibrio and salmonella bacteria which cause gastroenteritis and norovirus infection that is characterized by diarrhoea, vomiting, nausea, abdominal cramp etc. Hepatitis A is the most serious viral infection associated with the consumption of oyster and clams and been known since the 1960s. The largest reported outbreak occurred in China in 1988; almost 3 lakh persons were infected after consuming clams harvested from a sewage contaminated area.
Scombrotoxic poisoning that results from bacterial spoilage of tunny, mackerel and related fish is another factor for making seafood unsafe. Disrupted muscle liberates histidine from which histamine is formed, and this together with other toxins produces headache, palpitation, flushing and diarrhoea a short time after ingestion. This is not prevented by cooking the fish. An outbreak, affecting over 200 people, from canned tuna once occurred in the US. Global seafood consumption has more than doubled in the past 50 years, to over 20 kg per capita per year in 2104. As the demand for seafood rises, steps should be taken to ensure seafood is risk free.
Many commonly used foodstuffs naturally contain toxic principles in small amounts. The taboos and tradition operating in all communities have protected people from extremely toxic plants and animal products. Cyanogenic glycosides are phytotoxins which occur in as many as 2000 plant species, of which a number of species are used as food in some areas of the world. Cassava sorghum, stone fruits, bamboo roots and almonds are specially important foods containing cyanogenic glycosides. Cyanide is formed following hydrolysis of Cyanogenic glycosides that occur during crushing of the edible plant material either during consumption or during processing of the plant material. In humans, the clinical signs of acute cyanide intoxication can include rapid respiration, dizziness, drop in blood pressure, mental confusion, vomiting, diarrhoea. Death due to cyanide poisoning can occur when cyanide levels exceeds the limit an individual is able to detoxify.
Ingestion of large amount of fresh cabbage, raw soybean and the red scale of groundnut can prevent the normal functioning of thyroid gland due to the presence of goitrogens which do not allow the gland to take up adequate iodine for producing thyroid hormone. Soybean is the richest sources of vegetable protein but in the raw stage it contains a number of toxic principles which must be removed. Raw and partially cooked soybeans and flour contain trypsin inhibitor and hemagglutinins which are toxic protein.
Trypsin is the vital enzyme which help to digest proteins in the small intestine and trypsin inhibitor suppresses the activity of the enzyme. Hemagglutinins are known to cause clumping of red blood cells. Both these toxic factors are destroyed by heat. Pathogenic microbes proliferating in foods such as milk, meat and cereals produce highly toxic compounds during their growth. These toxins remain in food even after the bacteria are destroyed and may not be removed by cooking or processing. Industrial activities have recently concentrated on food. There are thousands of food additives such as flavourings, colourings, preservatives, emulsifiers and sweeteners present in the marketed processed food today. Some of the chemicals used are natural and approved but a great many are man-made and harmful. Plastic is used everywhere indiscriminately. It’s in bowls, wraps, and a host of bottles and bags used to store food and beverages. Studies have found that certain chemicals in plastic ~ plasticizers, coloring agents, stabilizers to heat and light, fire retardants and antioxidants ~ can leach out of plastic and into the food and beverages we eat.
Antibiotics have been a powerful force since the discovery of penicillin in the late 1920s. Use of antibiotics has not been restricted to humans. Nor is it limited to diseases only. To cater to the growing demand, even poultry farmers add antibiotics in low doses to chicken and turkey feed, antibiotics promote growth in poultry by helping them to maintain healthier digestive systems. Indiscriminate and routine use of antibiotics in low doses during chicken’s short-cycle of 35–32 days for faster growth promotes the growth of anti-microbial resistance (AMR) bacteria. By some estimates, more than 75 per cent of poultry is contaminated with E.coli, much of it resistant to antibiotic drugs. Handling bacteria-ridden food could spread E.coli to the urinary tract.
The most noxious problem is food adulteration, when unscrupulous people add bad stuff to food for profit. In our country milk is mixed with urea. Harmful azo dyes are being used for making the egg and chicken a deep yellow/orange. A few years ago, melamine-contaminated milk killed babies in China. Horsemeat sold as beef sent Europe into a tizzy. A study by Delhi-based non-profit Centre for Science and Environment (CSE) has found that packaged food items have genetically modified (GM) ingredients in them. In his book, Physiologie du Gout, the 18th century French lawyer and politician Anthelme Brillat- Savarin said, ‘Tell me what you eat and I will tell you what you are.’ This probably holds true for a developed country. But in a poor and developing country like ours, where even we don’t know what is in our food, how will we tell others what we are?
The writer is a retired IAS officer